Method and apparatus for translating ultrasonic energy

ABSTRACT

A novel method and apparatus for converting vibratory energy in the radial direction into vibratory energy in the longitudinal direction by forming a tapered surface on a piezoelectric element and attaching it to a mating transition member which has a corresponding tapered surface.

United States Patent 1191 Murry May 22, 1973 [54] METHOD AND APPARATUSFOR [56] References Cited TRANSLATING ULTRASONIC ENERGY UNITED STATESPATENTS [76] Invent Edward West 2,565,158 8/1951 Williams ..310/8.7Palos Park, 60494 3,058,014 10/1962 Camp ..3l0/8.7 22 F1 d: .24 1972 I 1l 6 Jan Primary Examiner-J. D. Miller [21] Appl. No.: 220,096 AssistantExaminerl\ iark O, Budd Attorney-Carlton Hill, Benjamin H. Sherman, 52us. 01 ..310/s.3, 259/010. 41, 259/010. 44, Charles 310/82, 310/9.l 57ABSTRACT [51] Int. Cl. ..H04r 17/00 58 Field of Search ..3 10/8, 8.2,8.3, A methd and apparatus mm/flung 310/8 7 9 l 9 259/ R DIG l5 DIG 41ry energy in the radial direction into vibratory energy in thelongitudinal direction by forming a tapered surface on a piezoelectricelement and attaching it to a mating transition member which has acorresponding tapered surface.

13 Claims, 12 Drawing Figures ,,,I,1 I I! [,grj/ Z3 5 E ((14 55 PatentedMay 22, 1973 2 Sheets-Sheet I METHOD AND APPARATUS FOR TRANSLATINGULTRASONIC ENERGY BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates in general to ultrasonic transducers and inparticular to an improved apparatus and method of converting vibratoryultrasonic energy from a radial to a longitudinal direction.

2. Description of the Prior Art It has been known to propagateultrasonic vibratory energy into cleaning fluids or other liquids ormaterials, but this has generally required singleblocks of fairlyexpensive ceramics which are fabricated by complex manufacturingtechniques and which must be onequarter wave length long. Also,Langevin-type sandwiches having a compositemass load of one-half wavelength have been used for generating of longitudinal ultrasonicvibrations. The Langevin sandwich method does not require an excessivelyhigh'operating voltage and is extremely efficient. This method also doesnot require excessive amounts of ceramic material.

It has also been known to utilize ring-or disc-type ceramicpiezoelectric transducers which vibrate in many complex modes and whichmay be polarized to emphasize one or the other of-themodes as desired.If the radial mode is selected, itis possible to use a lower,'moreefficient, frequency for most purposes which is also more effective inthe utilization of the energy. The problem is to convert theradial-motion of the transducer into up and down longitudinalvibrations. Previously this has not been possible and usually thin,fragile discs of a fairly low radial vibratory frequency but of a veryhigh longitudinal frequency have been connected to the bottom ofcleaning tanks or transformation concentrators by cementing and therebyhopefully vibrating the attached structures usually in someform ofinefficientflexural vibration. However, the vector-forces at theinterface are very unfavorable and low efficiency and low effectivenessin conversion of the energy has resulted. Where horn devices have beenused, very little of the required longitudinal vibrations have beenobtained.

SUMMARY OF THE INVENTION The present invention relates to apparatus andmethod of directly converting radial vibrations to longitudinalvibrations by utilizing a radially polarized ring piezoelectrictransducer which allows low voltage and low frequency design and isinexpensive, and, which has a tapered surface that mates with thetapered surface of a translation member which is attached to the loadsuch that the radial vibrations of the crystal are converted intolongitudinal vibrations and supplied to the load.

It is another object of the invention to provide means and method forcoupling sonic or ultrasonic energy directly and efficiently into a testobject or fluid with a simple and inexpensive transducer.

Other objects, features and advantages of the invention will be readilyapparent from the following description of certain preferred embodimentsthereof taken in conjunction with the accompanying drawings althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts of the disclosure, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view of a tank containinga liquid with a V4 wave transducer of the.prior art attached to itsbottom;

FIG. 2 is a view of a tank with a prior art Langevin type transducerconnected to its bottom;

FIG. 3 is a view of a tank using the device disclosed herein;

FIG. 4 illustrates a horn using the device disclosed herein;

FIG. 5 is an exploded view of the novel translating transducer of thisinvention asused in FIGS. 3 and 4;

FIG. 6 is an enlarged detailed view of the annular crystal andtranslation member of this invention used in FIGS. 3 or 4;

FIG. 7 is a sectional assembly view through the invention as used inFIGS. 3 and 4;

FIG. 8 illustrates the invention connected to an impedance transformerassembly as shown in FIG. 4;

FIG. 9 is asectional view of a modification of the invention as appliedto a pulser for N.D.'I. (Non- Destructive Testing);

FIG. 10 is a sectional view of a modification of the invention as usedin a submersible transduceror sonar;

FIG. 11 is an outside perspective view of the submersible transducer;and

FIG. 12 is .a'sectional view of a modified form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates-a structureof the prior art wherein a tank 10 contains a liquid 11 and to which aceramic transducer 12 has been mounted on the bottom thereof. Thetransducer 12 is made of expensive ceramic and must be fabricated bycomplex manufacturing techniques and must be about one-quarter wavelength long. Such structure is capable of generating longitudinalvibrations but is expensive and complex.

FIG. 2 illustrates another prior art device wherein two ceramictransducers 16 are mounted between a pair of metal members 13 and 14 tofonn a Langevin sandwich and the structure is attached to the bottom ofthe tank 10. Such structure utilizes a composite mass load of one-halfwave length and does not utilize as much expensive ceramic material asthe embodiment of FIG. 1 or as high a voltage.

It has been known in the prior art that a ringor disctype ceramicpiezoelectric transducer has many comforth vibrations into longitudinalup and down vibra-' tions. i

In the prior art, usually thin, fragile discs of a fairly low radialvibratory frequency have been utilized similarto the disc 17 attached tothe container 10 in FIG.

3. Such modified discs have a fairly low radial vibratory frequency but.a very high longitudinal frequency and have been merely cemented to thebottom of the tank 10, or alternatively, have been connected, quiteuselessly, asshown in FIG. 4 to a transformation concentrator such as 18in FIG. 4 wherein an unmodified crystal 21 is attached by cement 19 tothe large end of the truncated conical concentrator 18. In the structureof FIG. 3 vibrations in a complex mode have occurred in the form ofinefficient flexural vibration. Since the vector forces involved at theinterfaces are very unfavorable, low efficiency and effectiveness haveresulted. Also, in the transformer concentration born 18 of FIG. 4, verylittle, if any, of the desired longitudinal vibrations are obtained.

FIGS. -7 illustrate one embodiment of the present invention forefficiently converting radial vibrations to longitudinal energization.

FIG. 5 illustrates a transition member 23 of generally truncated conicalshape which has its largest diameter base attached to the bottom 22 ofthe tank 10. It may be attached by cement 29 or alternatively by bolts27 which pass through openings 28 in the bottom of the tank 22 and arereceived in mating threaded openings 24 formed in the transition member23. The transition member 23 is formed with a central threaded opening26 for a purpose to be described later. The taper of the outer surface25 of the member 23 may be 45. The transition member 23 may be made ofaluminum, as for example 7075-T6 aluminum, which has acoustic impedancethat approximates that of the piezoelectric material. An annularpiezoelectric crystal member 31 is formed with a mating tapered conicalopening 32 which fits over and engages the surface 25 of the transition23. The surfaces 25 and 33 are machined or ground to a high classultrasonic fit so as to make intimate contact for high ultrasonicefficiency. The ring 31 is also attached to the bottom of the tank bycement 34 and an electrically conducting washer 36 is mounted on thecrystal 31. The washer 36 has a central opening 37 which aligns with theopening 32 of the crystal. A portion 38 extends and forms an electricalcontact for the side of the crystal away from the bottom 22 of the tank.A grommet 39 is formed with a central opening 41 and a shoulder 42 andis received in the opening 37. The grommet 39 is made of insulatingmaterial and the opening 41 is smaller than the smallest diameter of theopening 32 in the crystal 31. A second electrical contact 43 is formedwith an extension 46 to form a second electrical contact and is formedwith a central opening 44 through which a compressive bolt 47 extends.

FIG. 7 illustrates the structure in assembled relationship and it is tobe noted that the tab 46 provides electrical contact through the bolt 47and the transition member 23 to the tapered face 33 of the crystal andthus an electrical potential can be applied to the crystal between themembers 36 and 43.

FIG. 6 is an enlarged exploded view of the crystal 31 and the transitionmember 23.

When electrical power is applied to the terminals 38 and 46 the crystal31 vibrates in the radial mode and these vibrations impinge on thetransition member 23 and are converted to longitudinal vibrations due tothe longitudinal component of the radial vibrations which occur on thesurfaces 33 and 25. Thus the radial vibratory energy which can begenerated at a much lower frequency directly and efficiently isconverted into energy in a longitudinal mode as shown. Efficientlongitudinal vibrations are applied to the bottom 22 of the tank.

FIG. 8 illustrates an embodiment wherein the longitudinal vibrations areapplied to a transformer concentrator or impedance transformer 51 whichis sometimes designated as a horn. A tool may be threadedly attached toa small threaded portion of the generally conical shaped born 51 and thetransition member 23 and crystal 31 may be attached to the large baseend of the horn 51. The electrical contacts 36 and 43 and insulatingmember 39 with compression bolt 47 may be provided in the same fashionas in FIG. 7. The members 23 and 31 may be attached to the base of themember 51 by cement or in other suitable fashion. Thus the structure ofFIG. 8 provides for high energy longitudinal vibrations from the end 53of the horn.

FIG. 9 illustrates a small test transducer of the flawprofile form forapplying sonic energy to test specimens such as required inNon-Destructive Testing (NDT). In this structure an output member 58 isformed with a conical coupling end 60 which mates with the conicalsurface of a crystal 67. The transition member 58 may be formed with asonic concentrator end 59. An electrical insulator washer 68 is held bythe compression screw 69 and bears against the crystal 67 and member 58.A case member 56 encloses the crystal and has a supply lead with ashield 71 which has a shielded grounded conductor 63 which is connectedelectrically to the compression bolt 69 and thus to the transitionmember 58. A second lead extends through the insulating member 8 and iselectrically connected to a surface of the crystal away from thetransition member 58. Member 58 is supported by disc 100 from member 56.

In operation, electrical energy is applied to the crystal through theleads and the crystal oscillates in radial direction and theseoscillations are converted into longitudinal oscillations in thetransition member 58 and applied to the load.

FIG. 10 illustrates a submersible type transducer comprising a housing78 in which is mounted a diaphragm 81 which is sealed by an O-ring tothe housing 78. A transition member 82 is attached to the diaphragm 81and an annular piezoelectric ring member 83 is formed with a beveledsurface and mates with the beveled surface of the transition member 82.An insulating disc and conducting washer 84 are mounted adjacent thecrystal 83 and a compression bolt 86 is threadedly received in thetransition member 82 to hold the assembly together. Electrical supplylead 91 has conductors 88 and 89 respectively connected to thecompression bolt 86 and the conducting washer 84.

FIG. 11 illustrates the submersible transducer 78 in perspective viewwith the supporting electrical lead 91.

FIG. 12 illustrates a modification of the invention wherein a load 93has a transducer 94 attached which has two 45 faces. An annular shapedceramic crystal 96 is bonded to the load 93 by cement 97 and is formedwith two tapered 45 faces 98 and 99. An external transition ring 104mates with the face 98 of the crystal 96. A central transition member101 shaped with atapered edge 102 mates'with the face 99 of the crystal96. Conductor ring 106 is attached to the large end of the ceramiccrystal 96 and electrical lead 116 extends through an insulating disc108 and is attached thereto. Compression bolts 111, 112 and 113 attachthe insulating ring 108 to the transition members 104 and 101.Electrical lead 114 is connected to the compression bolt 112 whichconnects to member 101 and applies ground potential to the crystal 96through the member 101. The second lead 116 extends through the member108 and connects to ring 106 and provides the second electrical input tothe crystal 96.

In this embodiment the crystal is caused to osciallate transverselyrelative to FIG. 12 and this energy is converted into longitudinalenergy and supplied to the load 93 due to the tapered surfaces 98 and99. Since there are two surfaces of transition from radial tolongitudinal energy, the efficiency and amount of radial energy suppliedby the crystal 96 is substantially increased.

It can be seen that this invention provides for a new and improvedpiezoelectric transducer although it has been described with respect topreferred embodiments it is not to be so limited as changes andmodifications may be made therein which are within the full intent andscope as defined by the appended claims.

What I claim is:

1. Apparatus for converting radial vibrations in a piezoelectric memberto longitudinal vibrations comprismg:

a surface of said piezoelectric member tapered relative to radialvibrations of said member;

a transition member mounted to said piezoelectric member and formed witha mating tapered surface and engageable with said tapered surface ofsaid piezoelectric member; and

means for generating radial vibrations in said piezoelectric member.

2. Apparatus according to claim 1 wherein said piezoelectric member isannular in shape and said tapered surface is formed about the centralopening and said transition member is conical so as to mate with saidtapered surface.

3. Apparatus according to claim 1 wherein said piezoelectric member isannular in shape and said tapered surface is formed about said outeredge thereof opening and the first and second tapered surfaces taperedin directions such that longitudinal vibrations in said first and secondtransition member extend in the same direction.

5. Apparatus according to claim 1 wherein said transition member isformed of metal.

6. Apparatus according to claim 5 wherein said transition member isformed of aluminum.

7. Apparatus according to claim 1 wherein a load is attached to saidpiezoelectric and transition members.

8. Apparatus according to claim 7 wherein said means for generatingradial vibrations in said piezoelectric member includes a firstelectrical conductor connected to said piezoelectric member on the sideaway from said load and a second electrical conductor connected to saidtransition member.

9. Apparatus according to claim 8 wherein said first electricalconductor is washer-shaped.

10. Apparatus according to claim 1 wherein a conical shaped horn isattached to said piezoelectric and transition members to receivelongitudinal vibrations therefrom.

11. Apparatus according to claim 1 wherein a diaphragm is attached tosaid piezoelectric and transition members, and a housing encloses saidmembers and is formed with an opening covered by said diaphragm.

12. Apparatus according to claim 1 wherein said transition member has aportion of reduced cross section at its end away from said matingtapered surface.

13. The method of converting radial vibrations in a piezoelectric memberto longitudinal vibrations comprising the steps of:

forming a surface on said piezoelectric member which is tapered relativeto radial vibrations therein;

forming a transition member with amating tapered surface; and

connecting said piezoelectric and transition members together with thetapered surfaces together to convert radial vibrations into longitudinalvibrations.

1. Apparatus for converting radial vibrations in a piezoelectric memberto longitudinal vibrations comprising: a surface of said piezoelectricmember tapered relative to radial vibrations of said member; atransition member mounted to said piezoelectric member and formed with amating tapered surface and engageable with said tapered surface of saidpiezoelectric member; and means for generating radial vibrations in saidpiezoelectric member.
 2. Apparatus according to claim 1 wherein saidpiezoelectric member is annular in shape and said tapered surface isformed about the central opening and said transition member is conicalso as to mate with said tapered surface.
 3. Apparatus according to claim1 wherein said piezoelectric member is annular in shape and said taperedsurface is formed about said outer edge thereof and said transitionmember is annular in shape and said mating tapered surface is formedabout the central opening thereof.
 4. Apparatus according to claim 3wherein said piezoelectric member is formed with a second taperedsurface about the central opening, a second conicaL transition membermounted within said central tapered opening and the first and secondtapered surfaces tapered in directions such that longitudinal vibrationsin said first and second transition member extend in the same direction.5. Apparatus according to claim 1 wherein said transition member isformed of metal.
 6. Apparatus according to claim 5 wherein saidtransition member is formed of aluminum.
 7. Apparatus according to claim1 wherein a load is attached to said piezoelectric and transitionmembers.
 8. Apparatus according to claim 7 wherein said means forgenerating radial vibrations in said piezoelectric member includes afirst electrical conductor connected to said piezoelectric member on theside away from said load and a second electrical conductor connected tosaid transition member.
 9. Apparatus according to claim 8 wherein saidfirst electrical conductor is washer-shaped.
 10. Apparatus according toclaim 1 wherein a conical shaped horn is attached to said piezoelectricand transition members to receive longitudinal vibrations therefrom. 11.Apparatus according to claim 1 wherein a diaphragm is attached to saidpiezoelectric and transition members, and a housing encloses saidmembers and is formed with an opening covered by said diaphragm. 12.Apparatus according to claim 1 wherein said transition member has aportion of reduced cross section at its end away from said matingtapered surface.
 13. The method of converting radial vibrations in apiezoelectric member to longitudinal vibrations comprising the steps of:forming a surface on said piezoelectric member which is tapered relativeto radial vibrations therein; forming a transition member with a matingtapered surface; and connecting said piezoelectric and transitionmembers together with the tapered surfaces together to convert radialvibrations into longitudinal vibrations.